|M.Sc Student||Sverdlov Roni|
|Subject||Nanoparticle-in-Microparticle Drug Delivery System|
of an Antiretroviral Combination
|Department||Department of Materials Science and Engineering||Supervisor||Professor Alejandro Sosnik|
|Full Thesis text|
Chronic antiretroviral (ARV) therapy is required to maintain viral suppression and reduce disease progression in the human immunodeficiency virus (HIV) infection. Even after the implementation of the Highly Active Antiretroviral Therapy (HAART), one of the main causes of therapeutic failure in anti-HIV therapy is the poor aqueous solubility of hydrophobic ARVs in the intestinal fluids that reduce their oral bioavailability. Darunavir (DRV) is a gold-standard ARV of the protease inhibitors (PI) family used in the anti-HIV cocktail. PIs dissolve under the low pH conditions of the stomach though are poorly water-soluble in the neutral medium of the small intestine. To improve the oral pharmacokinetics (PK), PIs are co-administered with the boosting agent ritonavir (RIT), a drug that inhibits first-pass metabolism in the liver and thus, increases the oral bioavailability of the PI. However, its PK remains suboptimal. Nanotechnology-based approaches such as drug nanonization offer unique opportunities to improve the dissolution rate of hydrophobic ARVs and increase their intestinal absorption. However, we anticipate that unless protected in the stomach, PIs will dissolve under gastric pH conditions and re-precipitate upon reaching intestinal pH. This uncontrolled dissolution-re-precipitation process due to the pH-dependent solubility of PIs might ‘erase’ the effect of nanonization on the dissolution rate. To tackle this challenge, in this thesis, we designed, produced and fully characterized a novel Nanoparticle-in-Microparticle Delivery System (NiMDS) comprised of pure nanoparticles of the first-line PI DRV and its boosting agent RIT. For this, a clinically relevant combination of pure DRV and RIT nanoparticles was synthesized by a sequential nanoprecipitation/solvent diffusion and evaporation method employing sodium alginate (ALG) as viscosity stabilizer. Solubility studies demonstrated that the nanonization increases the dissolution rate and solubility of DRV and RIT under intestinal pH. Then, pure nanoparticles were encapsulated within calcium alginate/chitosan microparticles that were film-coated with a series of poly(methacrylate) copolymers. This coating ensured full stability under gastric-like pH and sustained drug release under intestinal one. The swelling of film-coated microparticles was substantially lower than that of the uncoated ones. The swelling was also substantially lower under gastric pH in comparison to intestinal pH. Furthermore, release studies of DRV in vitro were promising in the sense that under gastric pH the release rate was marginal, whereas under intestinal pH the drug was released much faster. Finally, PK studies conducted in albino Sprague Dawley rats showed that DRV/RIT-loaded NiMDSs containing 17% w/w drug loading based on dry weight significantly increased the oral bioavailability of DRV by 2.3-fold with respect to both the unprocessed and the nanonized (though not microencapsulated) DRV/RIT combinations that showed almost identical performance, highlighting the relevance of the microencapsulation to capitalize on the drug particle size reduction in this family of ARVs. These data confirmed the limited advantage of drug nanonization to improve the oral PK of PIs and highlights the potential of our novel delivery approach to improve the oral PK of poorly water-soluble drugs displaying pH-dependent solubility.